The conventional heat-insulation structure which has been used in automobiles under the conditions of vibrational stress and high temperatures of over 500.degree. C, represents a structure using a ceramic fiber (of A1.sub.2 O.sub.3 -SiO.sub.2 base mineral) as the heat-insulation material. In long service under vibration, however, such a structure gets pulverized with its heat-insulation layer shrunk and its heat-insulation performance seriously reduced. Meanwhile, the filling of a 2-4.sub.mm void with ceramic fiber has been technically and economically controversial. These are the points for which an improvement has been demanded.
For application under low temperatures (less than 80.degree. C), a heat-insulation double tube made of polystyrol resin has been invented for mass production of heat-insulation tubes for low-temperature service. Being aimed not at anti-vibration, but at low manufacturing, cost, this invention has the drawback of being inferior in resistance to heat and vibration.
Thus, there is no anti-vibration heat-insulation structure known that can serve under high temperatures.